Gels

Question 1

What are gels?

Answer 1

Non-fluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid

Question 2

What are they characterised by?

Answer 2

Their ability to develop rigid molecular network + swell when solvated

Question 3

Why do gels swell?

Answer 3

Solvent infiltration into molecular network = unfolding + expanding the molecular network

Question 4

What is a Type I gel?

Answer 4

Chemical gel

Question 5

Describe a Type I gel

Answer 5

Irreversible polymer network
Covalently cross-linked
Often uses a covalent cross-linker

Question 6

What is an example of a Type I gel?

Answer 6

Polyacrylamide gel

Question 7

What is a Type II gel?

Answer 7

Physical gel

Question 8

Describe a Type II gel

Answer 8

Reversible polymer network
Weak intermolecular bonds
Sol-gel transition in response to specific stimulus

Question 9

What is an example of a Type II gel?

Answer 9

Agarose gel

Question 10

What is a pharmaceutical gel?

Answer 10

Drug entrapped in gel matrix
Topical administration

Question 11

What are the indications of pharmaceutical gel?

Answer 11

Analgesic
Anti-inflammatory
Anti-bacterial
Anti-fungal
Local anaesthetic

Question 12

What are the basic components of a pharmaceutical gel?

Answer 12

Drug
Solvent
Gelling agent

Question 13

What may pharmaceutical gel also contain?

Answer 13

Co-solvent
pH regulator
Preservative
Penetration enhancer

Question 14

What are gels formed from?

Answer 14

Sols

Question 15

What is a sol-gel transition?

Answer 15

Occurs at the gel point
Gel point = point of incipient polymer network formation

Question 16

What does the gel point depend on?

Answer 16

Chemical composition of gel formation